All computers need memory. It provides a workspace into which the processor can hold data and rapidly modify it. While the hard drive performs much the same job, the speed of RAM makes it ideal for intensive tasks and time sensitive applications. There are many different brands and memory products, so what are the critical aspects in getting the right stuff for your PC?
Basic Types Of RAM
Very old computers used SDRAM (synchronous dynamic random-access memory), and that was in turn replaced with DDR (double data rate RAM), and then DDR2 and DDR3. Unless you own a PC that's more than six years old, the chances are that it uses DDR3, because almost without exception that's the current standard.
For home computer, use they come m two forms: the 204-pin SO-D1MM for laptop use and the 240-pm DIMM that desktop computers can utilise.
In general, most laptops have the memory interfaced in a way that means the SO-DIMM modules are used in a single-channel mode, allowing you to add a 4GB module to an existing 2GB system, slots allowing.
On desktop PCs, the modules can be organised into dual-, triple- or even quad-channel sets, so you need to use multiple modules to get the best results. Mixing mod Lies with different speed and timing specifications isn't advised. Match what memory you already haw or replace them with new modules to maintain optimal system stability.
Speed, SPD And Timings
Those trying to pick new RAM modules are bombarded with SPD tables and timings, most of which are entirely incomprehensible to the uninitiated.
It doesn’t help that RAM makers use two entirely different ways to describe speed, detailing the top dock speed and also using FC3-12800 type notation.
Before you get totally confused, first check with your motherboard or laptop maker, and see vvhat speed modules they recommend. If they say PC3-10500 (1333MHz) modules, then ideally use those.
Faster modules can usually run at slower settings, but that is a waste of money. Getting the crazily specified ones that can achieve 2132MHz (PC3-17000) might seem a good idea, but only if your system can use them correctly.
In addition to dock speeds, all modules have a timing spec, like 10-10-10-10-28. This defines how rapidly the module can react, and the term 'latency' is often used. The smaller these numbers, the better quality the module - it's that simple. However, you need to understand that as the modules go faster (above 1333MHz, say), those timing numbers increase by default.
The most important number is the very first mentioned, or it can be prefixed with 'CL' for CAS latency. A CL of 9 means that it takes nine clock cycles for the module to respond to a request, so smaller numbers indicate a faster response.
What sightly complicates things is that modules might offer a CL of 9 at say 800MHz. and CL 12 1866MHz. The ability of the module to make these adjustments is controlled by a list built into the module by the manufacturer, called the SPD (serial presence detect).
Many memory brands will detail the SPD of a given module - a simple look-up chart for timings against clock speed. Having an extensive SPD defined allows a module to run either with a high clock speed with loose timings, or a slower clock with tighter ones, or various settings in-between. I could explain what each of the numbers represents, but it's not critical in determining which of two possible products is superior.
It's also worth noting that while stylish heat spreaders do look nice, unless you intend to overdock, they're not a necessity, and not a guarantee of the quality of RAM chips under them.
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| Becauce the notch is in a different place on each RAM type, its almost impossible to put one type in a slot made for another |
Performance Versus Cost
Once you understand why some memory costs more, the next obvious question must logically be whether faster modules are worth the extra. That depends on whether you wish to overdock or get the best performance out of a system, because for most users, standard specification memory is fne. Faster tunings on a system running at stock speeds might get you 2-3% more speed, but it will usually take benchmarks to see the difference.
If you tweak your CPU to a higher clock rate, that usually increases the dock on which memory access is based, and the only way that's not going to destabilise the PC is if you have high spec memory.
There's also a thought, one that rm happy to accept, that using better quality parts are a good plan, because if they're operating well within their specification, they'l be extra reliable. That is probably true, and if you have stability issues, better memory might well help.
In the end, it all comes down to the price difference, and with the very low cost of memory these days, it could well be worth getting something better.
Cost Versus Capacity
One of the questions I'm often asked is 'How much memory is enough?'. That's a realty tough one, because the answer to that is very dependent on what you use your PC for and the applications you intend to run.
However, one simple rule is that if you run a 32-bit OS. like the original version of XP, or the 32-bit versions of Vista, 7 or Windows 8. then don’t put more than 4GB in the system. Putting more won't damage it, but these operating systems can't address any more than 4GB even if it exists. To get access to that RAM, you'll need a 64-bit OS, and most people wouldn't notice the dfference between 4GB an 8GB in the same system. Having more RAM should be a real advantage, but the operating systems of our day aren't wett designed to use more than 4GB or 8GB effectively, and it usually gets used just to cache active files.
Unless you intend to run a massive database or file server. I wouldn't spend excessively to fill up your memory slots just because the/re available.
Final Thoughts
Picking the right memory for a system isn't straightforward, so it* best to do research before spending. If you have less than 4GB, then more can't hurt, and it only costs a few pounds these days. If you intend to buy a new system, it's also worth considering what adding the RAM now might cost compared to adding it later. Exotic memory is lovely to have, but the majority of systems with it in don't exploit the potential it offers.
Next time, I'll talk about what comes after DDR3, and how it might impact on the performance we've come to expect.
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